1. Field of the Invention
The invention relates to a single wafer type substrate cleaning method and a single wafer type substrate cleaning apparatus, more particularly to a single wafer type wet cleaning technique or system for applying a cleaning treatment to substrates such as semiconductor wafers one by one during the fabrication process as well as certain devices such as electronic parts and the like.
2. Prior Art
A so-called batch type wet cleaning system has been the principal method of cleaning substrates such as semiconductor wafers (hereinafter referred to simply as “Wafers”), whereby wafers stored in a carrier cassette are immersed in sequence in wet bench type cleaning baths arranged in series, or wafers are directly immersed in the cleaning baths through a transfer unit without being stored in a carrier cassette. However, semiconductor devices have reached the sub micron age, in that they are now micro-fabricated and highly integrated, such that the face of wafers has recently required a very high degree of cleaning density, and wafers which are not stored in a cassette have to be wet-cleaned individually in a sealed cleaning housing. To this end, a so-called single wafer type wet cleaning system intended to meet the requirement of a higher cleaning density has been developed and proposed.
Under the single wafer type wet cleaning system, wafers can be cleaned with the use of a simple and compact cleaning apparatus in a relatively clean atmosphere where particles and the like do not settle or remain on the face of the wafer. This system is therefore practical to use for small scale production.
Generally, under the single wafer type wet cleaning system, a cleaning treatment is applied to the front face, i.e., the upper side surface of the wafer by various chemical fluids in a predetermined order. In the process, the chemical fluids supplied flows to the back face of the wafer, thereby possibly contaminating the back face of the wafer. If the back face of the wafer is contaminated, the handling jig for the wafer, e.g., the robot hands of a schalar type robot, also become contaminated, and as a result, other wafers which are handled by the same robot hands naturally also get contaminated.
For the foregoing reason, a technique for preventing the chemical fluid(s) from flowing to the back face of the wafer has become immensely desirable, and the device shown in FIG. 7 providing such technique has been proposed under Japanese Patent Laid Open Publication No. 2000-343054 (hereinafter referred to as the “Chemical Fluid Flowing Around Prevention Technique”).
Under the Chemical Fluid Flowing Around Prevention Technique, chemical fluid is supplied to the front face Wa of a wafer W while it is rotatably supported by a wafer rotary section “a”, and simultaneously a certain gas is supplied from an annular nozzle “b” under the wafer W so as to float the wafer W while it is prevented from sliding sideways by a supporter member “c”, so that the chemical fluid which has flowed from the front face Wa of the wafer W to the back face Wb thereof is blown off as shown in FIG. 7(B).
However, the system of blowing off the chemical fluid through the supply of a gas prevents the back face Wb of the wafer W from being cleaned, thereby making it difficult to completely avoid contamination of the wafer. Accordingly, a further improvement of the system is desirable.